Although barley is used extensively as a food
in some areas of the world, few data are available on its
nutritional qualities and dietary bulk in weaning foods.

As the dietary bulk of traditional weaning
foods is a major constraint in providing enough food to small
children [1], in the previous paper [2] we examined the
dietary-bulk properties of barley-based gruels. Our findings
indicated that gruel made from ordinary barley flours, especially
when highly refined, is inadequate as a source of energy for
small children, but that, if the barley is germinated or if a
small amount (1%) of barley malt is added to ungerminated flours,
gruels with acceptable energy densities can be produced.

The capacity of a weaning diet to meet the
protein and energy requirements of infants depends, of course, on
its nutritional qualities as well as on its dietary bulk. This
paper describes the nutritional quality of barley gruels. The
effects of germination, refining, and the addition of malt were
also examined by chemical analysis and by rat bioassay.

The nutritional quality of cereals is likely to
vary considerably between different varieties, such as may be
grown in developing countries. Ethiopia, for instance, is known
for the diversity of its native barley types, and the first
highlysine variety identified was an Ethiopian line [3]. Both a
high-lysine barley and a standard variety were used in this
study.

Materials and methods

As reported in the previous paper [2], barley
of the high-lysine variety Ca 700202 was used. It was milled into
three different flours: wholemeal, semi-refined, and refined.
Flours were also produced from grain germinated for three, five,
or seven days. For comparison, a refined flour was produced from
a normal barley variety, Triumph. The procedures used to make the
different flours are outlined in the previous paper. Gruels were
prepared from the ungerminated flours, from the germinated
flours, and from the ungerminated flours mixed with 1% (dry
basis) of the flour made from barley germinated for seven days.
The dry matter contents of the gruels were those found to result
in acceptable viscosity, as described.

After being cooked in a pot, the gruels were
cooled to 40 °C, frozen immediately in liquid nitrogen, and
Iyophilized.

Analytical methods

The two barley varieties and the flours were
analysed for moisture [4], ash [5], protein (N x 6.25) [6], and
fat [7]. Starch content was determined as described by Bach
Knudsen et al. [8]. Insoluble and soluble dietary fibre were
determined by the procedure of Asp et al. [9]. Sugar was measured
as described by Jacobsen [10]. Energy was determined by bomb
calorimetry (IKA-O 400, Janke and Kunkel).

Amino acid analyses were conducted according to
the procedure of Mason et al. [11], and tryptophan was determined
by high-performance liquid chromatography and fluorescence
spectrophotometry after hydrolysis with sodium hydroxide (S.
Bech-Andersen, personal communication, 1988). Zinc, copper, iron,
and calcium were determined by atomic absorption
spectrophotometry [ 12] and phosphorus by the colorimetric method
of Stuffins [13]. The content of physic acid was determined [14].

Animals and diets

Groups of five Wistar male rats weighing on
average 70 g were assigned to the different dietary treatments.
The mean weight of the groups at the beginning of the experiment
differed by no more than 1.0 g. The rats were housed individually
in plexiglass cages with stainless steel mesh bottoms in a
controlled environment (temperature 25 °C, relative humidity
50%, light-dark periods of 12 hours). Each rat received 10 g of
dietary dry matter and 150 mg of nitrogen daily. Water was
provided ad libitum. The diets were fed for eight days. Faeces
and urine were collected separately during the last five days;
body weight and food consumption were recorded. The faeces were
Iyophilized and ground in a mortar into a fine powder for
analysis.

The diets were prepared from the Iyophilized
gruels and formulated to contain 1.5% of dietary nitrogen. A
nitrogenfree mixture, consisting of autoclaved potato starch
80.7%, sucrose 8.9%, cellulose powder 5.2%, and soya bean oil
5.2%, was used to adjust the dietary nitrogen content. The diets
contained 3.7% of a mineral mixture and 1.5% of a vitamin mixture
on a dry-matter basis [16].

True protein digestibility (TD), biological
value (BV), and net protein utilization (NPU = TD x BV) were
measured. Corrections were made for endogenous excretion of
nitrogen in the faeces ( 1.7 mg nitrogen per gram of dry matter
consumed per rat) and in urine (76 mg nitrogen per five days per
rat) as described by Eggum [15]. Utilizable protein (UP = NPU x
protein content) was calculated.

Estimation of digestible energy was based on
the analysis of diets and faeces. Digestible energy (DE) of the
products was estimated by calculation, and corrections were made
for the digestibility of energy in the nitrogen-free mixture. In
a preliminary experiment, the DE of the nitrogen-free mixture was
found to be 90.0%.

The data from the animal experiment were
subjected to one-way and two-way analyses of variance, and
differences between groups were identified by Tukey's test [17].
The minimum level of statistical significance accepted was P <
.05.

Results

Effects of milling on composition

The composition of the barley flours and the
barleys from which they were prepared are shown in table 1. The
refined flours contained more starch and less of other nutrients
than the wholemeal. The protein content of the most refined flour
was reduced to 83% of that in wholemeal, but the amino acid
composition was not changed by the milling process (table 2). The
contents of minerals and physic acid were reduced to about 60% of
the corresponding levels in wholemeal (table 3). Calcium was the
mineral most severely affected by the process. Milling caused a
slight decrease in the energy content of the flours, because the
fat-containing germ was removed. The content of insoluble but not
of soluble dietary fibre was also reduced by refining

Germination increased the concentration of
sugar and decreased the content of starch and dietary fibre. The
effect increased with germination time. Otherwise there was no
major change in the content of most nutrients, including
minerals. The level of physic acid, however, was lowered
significantly by germination; thus, the germinated flours
contained only half as much physic acid as the ungerminated
semi-refined flour, with a comparable degree of refining. The
level of physic acid was similar whether the grains were
germinated for three, five, or seven days. Germination caused
only minor changes in amino acid composition; the content of
glutamic acid decreased, whereas the concentration of proline
increased.

Composition of high-lysine versus
normal barley

The high-lysine flour differed in composition
from the normal barley, having more protein and less starch. The
improved barley flour also had higher concentrations of several
amino acids, including Iysine and threonine, which were increased
by 38% and 22% respectively. The contents of the non-essential
amino acids glutamic acid and proline were lower. The high lysine
flour had a higher content of dietary fibre, but mineral contents
and the level of physic acid in the two refined flours were quite
similar.

Protein and energy utilization

The two-way analysis of variance showed that
true protein digestibility and biological value (or protein
quality), as measured in rats, increased slightly but
significantly with milling (table 4). The effect was quite small;
both protein digestibility and biological value were
approximately 3% higher in absolute value in the refined flour
than in the wholemeal. Germination resulted in a significant
increase of about 5% in protein digestibility and a corresponding
reduction in biological value. Adding 1% of malt, on the other
hand, had no effect on protein digestibility or quality.
Refining, germination, and malt addition had no consistent effect
on net protein utilization, which ranged from 74% to 82%, with
highest values in the refined flours.

There was no difference in the NPU of gruels
made of refined flour from the improved variety and the control
barley, because, although the high-lysine line had better protein
quality, its protein digestibility was less than that of the
conventional variety.

The amount of utilizable protein, however, was
very low in the control gruel because of the low protein level of
the flour. The content of utilizable protein in the high-lysine
gruels varied between 9.0% and 10.3%; it was unaffected by
germination or the addition of malt.

The digestibility (%) of the energy increased
as a result of refining as well as of germination (table 5). It
was not affected by the addition of malt. The highest value, 93%,
was found for gruel made of reinfed normal barley. The amount of
digestible energy (calories per gram), determined on a dry-matter
basis, varied little.

Discussion

Effects of refining

Milling decreased the concentration of
nutrients in the flours with the exception of starch and sugar.
The changes during preocessing of the high-lysine barley into
flour resembled those occuurring during refining of normal barley
and other cereals [18]. On one hand, refining removes dietary
fibre and antinutritional factors such as phytic acid. On the
other hand, it greatly reduces the levels of vitamins and
minerals and lowers the protein content.

Refining caused an increase in protein
digestibility as well as in protein quality (biological value).
This is probably because the protein digestibility and the
availability of amino acids of the outer layers are low compared
to the endosperm [18]. The effect was small, however, and there
was no great difference in the amount of utilizable protein in
the flours of different degrees of refining. The increase in
energy digestibility with increasing degree of refining is caused
by a decrease in the content of fibre of low digestibility and a
simultaneous increase in the concentration of highly digestible
starch and sugar. The effect on energy digestibility was very
small, and there was no difference in the amount of digestible
energy between flours of different extraction rates.

More important perhaps than the effects on
protein and energy utilization are the effects of refining on
vitamin levels and mineral utilization. A highly refined barley
flour contains only 20%-30% of the B vitamins present in
wholemeal [19]. The mineral concentrations are also significantly
reduced by refining, but factors interfering strongly with the
utilization of some minerals, such as zinc, are removed as well.
Hence, in spite of a much lower content of zinc, refined barley
flour is probably a better source of available zinc than
wholemeal, which seems to be a poor zinc source |20|. Zinc is an
important mineral to consider, because zinc deficiency has been
reported to be common among malnourished children. Breast milk
may contain inadequate quantities, because the concentration
decreases with time, and zinc supplementation has recently been
shown to improve the nutritional rehabilitation of malnourished
children [21].

Effects of germination

Germination has been reported to increase the
Iysine content and improve the amino acid composition of cereal
grains [22; 23]. Its effect on protein quality (measured as
biological value or protein efficiency ratio [PER]) and
utilization, however, is unclear. Thus, in spite of an increase
in Iysine content, the PERs of ungerminated and germinated
millets were not significantly different [23]. Similarly,
Nattress et al. [24] reported that germination did not improve
the PER of seed mixtures. Brandtzaeg et al. [25] found a lower BV
in a malted millet-pulse mixture than in an unmelted mixture, and
attributed this reduction to the deterioration of some amino
acids during the roasting process of the germinated seeds. The
net protein utilization, however, was not affected by
germination. Taal et al. [26] found a small increase (6%-9%) in
the Iysine content of sorghum and millet during germination,
improved BV in sorghum but not in millet, and slightly improved
NPU values for both.

In our experiment the composition of amino
acids was largely unchanged by germination. The concentration of
glutamic acid decreased and that of proline increased, in
accordance with the results of Robbins and Pomeranz [22]. The
Iysine level apparently rose slightly during the germination
process, but the BV of gruels made from germinated barley was
lower than that of gruels prepared from ungerminated barley. The
reduction in the BV of the germinated gruels is probably due to
Maillard products formed during the cooking process. Germinated
flours have high levels of reducing sugars, facilitating the
formation of Maillard products. When Maillard products are
formed, Iysine is lost and protein quality reduced if Iysine is a
limiting amino acid [27]. In conclusion, because the protein
digestibility was increased by germination and the protein
quality reduced correspondingly, germination had no effect on
NPU. When malt was added at a 1% level, neither protein quality
nor utilization was affected, probably because Maillard compounds
are less likely to be formed when malt is used only as an
additive.

Germination improved the digestibility of
energy (%). Since the effect was small, however, there was no
difference in the amount of digestibile energy on a dry matter
basis (calories per gram) of the gruels made from germinated and
ungerminated flour. Adding malt had no effect on the content of
digestible energy of the barley gruels.

Germination did not affect mineral levels but
markedly reduced the content of physic acid. Because of the
reduction in physic acid, known to interfere with mineral
absorption, it is possible that the availability of minerals is
improved by germination [24]. However, it appears that physic
acid is not solely responsible for the low zinc availability of
unrefined barley flours [20], and the effects of germination on
mineral availability need to be examined further [24].

The levels of some vitamins increase during
germination while those of others do not [23-25]. For barley
there is no big difference in the vitamin contents of
ungerminated grains and malt [28].

Amino acid scores and protein intake

Leucine was the first limiting amino acid in
the highly sine flours, on the basis of the FAO/WHO/UNU [29]
amino acid scoring pattern for infants, followed closely by
Iysine. The scores for leucine varied between 67 and 71, with the
lowest value for the flour prepared after seven days of
germination and the highest value for the ungerminated wholemeal.
The normal barley flour was lowest in Iysine (52), followed by
leucine and threonine. Because of the enhanced levels of Iysine
and threonine in the improved variety, the BV of this variety is
exceptionally high compared with that of common cereal grains
[18].

All the gruels based on the high-lysine barley
provide a safe level of protein intake for infants and small
children. The calculations are based on the FAO/ WHO/UNU [29]
recommendations; the amino acid scores are used and corrections
are made for digestibility. Thus, if 60% of a one-year-old
child's energy intake is derived from barley gruels, the gruels
made from wholemeal, semi-refined, or refined flour will provide
94%, 87%, or 84% respectively of the child's total protein
requirement. If the barley is germinated for three or seven days,
the corresponding figures are 94% and 84%. In contrast, using the
same assumptions, normal barley provides only 45% of the total
protein requirement and thus does not provide a safe level of
protein intake for children under one year of age.

Conclusions

The capacity of weaning gruels to meet the
protein and energy requirements of infants depends on their
dietary bulk as well as their nutritional quality. In the first
part of this study [2], we found that if infants are fed
germinated barley gruel, or gruel made from ungerminated barley
with a small amount of malt added, they should be able to consume
sufficient quantities to fulfil their energy requirements, but
that ungerminated barley flours seemed to be inadequate as a
source of energy for small children, especially when highly
refined.

If sufficient quantities can be consumed, the
high-lysine barley, but not the normal barley, provides a safe
level of protein intake. In addition, although there are
differences in the energy and protein utilization of barley
gruels made from ungerminated versus germinated flours, and from
wholemeal versus refined flours, these differences are small and
are greatly superseded by the marked effects of germination and
refining on viscosity. The addition of malt seems to have no
effect on the nutritional quality of the gruels.

The effects of germination and refining on the
content and availability of vitamins and minerals also needs to
be determined.